HVACopediaNavien · Tankless water heater
MA.00 Cascade main unit confirmed
What the display is showing
Shown on the main heater when Diagnostic + Up (+) are held for more than 5 seconds, confirming it is set as the main unit of the two-heater cascade.
Applies to: NPN-160U/180U/199U, NPN-120E/160E/180E/199E
What to do
- Main unit hold Diagnostic + Up (+) for more than 5 s, MA.00 appears.
- Sub unit hold Diagnostic + Down (-) for more than 2 s, SL.01 appears.
- Main unit hold Diagnostic + Up (+) for 5 s again; displays return to temperature.
- To cancel, hold Diagnostic + Reset for 5 s on the main unit.
Settings for these units
Installation clearances (indoor / outdoor) · Navien NPN
| Side | Indoor: combustibles | Indoor: non-combustibles | Outdoor: combustibles | Outdoor: non-combustibles |
|---|---|---|---|---|
| Top | 6 in. (152 mm) | 2 in. (51 mm) | 12 in. (305 mm) | 2 in. (51 mm) |
| Back | 0 in. | 0 in. | 0 in. | 0 in. |
| Front | 6 in. (152 mm) | 6 in. (152 mm) | Panel 24 in. (610 mm); exhaust 24 in. (610 mm) | Panel 0 in.; exhaust 24 in. (610 mm) |
| Sides | 2 in. (51 mm) | 1/2 in. (13 mm) | 6 in. (152 mm) | 1/8 in. (3.2 mm) |
| Ground / bottom | 12 in. (305 mm) | 12 in. (305 mm) | 12 in. (305 mm) | 2 in. (51 mm) |
| Vent | 0 in. | 0 in. | - | - |
Room temp must stay between 32 F (0 C) and 120 F (49 C).
Outdoor models need a weather-rated disconnect switch for the 120 V supply.
Models that show this code
7 models in Navien NPN
Other codes on the same units
- Error icon Error indicator
- HEAT Recirculation started from remote
- Hot water recirculation icon Hot water recirculation indicator
- MAIN Remote asks for main/sub setting
- Master unit icon Master unit (cascade) indicator
- Preheat icon Recirculation schedule / preheat icon
- R&D information menu R&D information menu (Power off, key sequence)
- Recirculation mode display Recirculation mode display
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Source: Navien NPN-U/NPN-E Installation Manual, 5.2.1 Configuring the Communication Settings, p.58. Summarized in our own words; check the original manual for your model.
For licensed technicians. Gas, electrical and refrigerant work must be done by a qualified, licensed person. Shut off power and gas before servicing, never bypass a safety control, and follow the manufacturer’s manual for the exact model; it and local codes always take priority. HVACopedia is not affiliated with any manufacturer; brand and model names only identify the equipment.